Method of decarburization of slag in the electroslag remelting process

ABSTRACT

The introduction of an oxidizing agent, Fe3O4, FeO, Fe2O3, NiO, MoO2, CoO, Cu2O, Cr2O3, MnO, Mn2O3 or Mn3O4, or a combination thereof into slag in the bottom of the mold during the beginning of an electroslag remelting (ESR) process, but after the slag is fully molten and with an a.c. current at about 70 - 90 volts applied through the slag from the ESR consumable electrode in order to reduce the slag&#39;&#39;s carbon content to less than about 0.02%, the slag having a composition of about 40% CaF2, 30% CaO, and 30% Al2O2, and having obtained a carbon content of roughly 0.04 - 0.05% upon being melted in a slag furnace having a graphite or carbon brick lining prior to being introduced into the ESR mold, the oxidizing agent being introduced into the slag during the ESR process being about 0.2% of the slag by weight.

United States Patent [1 1 Scott, Jr.

[4 1 Sept. 16, 1975 METHOD OF DECARBURIZATION OF SLAG IN THE ELECTROSLAGREIVIELTING PROCESS [75] Inventor: William W. Scott, Jr., Parkesburg,

211 Appl. No.: 367,941

OTHER PUBLICATIONS Metals, 2 (10), March 1967, pp. 44, 45, 46, 47, 46Aand 48. Duckworth et al Electra-slag Refining, TN 685.5,E4D8, Chapman &Hall Ltd., London, Feb. 2, 1971, (p. 67 relied on).

Mitchell, Trans of Metallurgical Society of AIME, TNLM57, December,1968, Vol. 242, (pp. 2507-251 1 relied on).

British steelmaker, Sept. 1966, (pp. 48, 49 and 58 relied on).

Primary Examiner-L. Dewayne Rutledge Assistant Examiner-M. J. AndrewsAttorney, Agent, or FirmMason, Mason & Albright [5 7 ABSTRACT Theintroduction of an oxidizing agent, Pe o. FeO, Fe O NiO, M00 CoO, Cu O,Cr O MnO, M11 0 or Mn,,o,, or a combination thereof into slag in thebottom of the mold during the beginning of an electroslag remelting(ESR) process, but after the slag is fully molten and with an ac currentat about 70 90 volts applied through the slag from the ESR consumableelectrode in order to reduce the slags carbon content to less than about0.02%, the slag having a composition of about 40% CaF 30% CaO, and 30%A1 0 and having obtained a carbon content of roughly 0.04 0.05% uponbeing melted in a slag furnace having a graphite or carbon brick liningprior to being introduced into the ESR mold, the oxidizing agent beingintroduced into the slag during the ESR process being about 0.2% of theslag by weight.

28 Claims, 1 Drawing Figure METHOD OF DECARBURIZATION OF SLAG IN THEELECTROSLAG REMELTING PROCESS I BACKGROUND OF THE INVENTION Thisinvention relates to a method of decarburizing molten slag used in theelectroslag remelting process. More specifically it relates to aneffective method for removing carbon introduced into the molten slag byreason of being heated to a molten state in a furnace lined withgraphite or carbon bricks.

The electroslag remelting process essentially comprises the fusing froma consumable electrode of metal which is to be refined under a blanketof molten slag or flux. The consumable electrode is generally suspendedwithin a water cooled copper or steel mold and molten slag is introducedinto the mold and acts as an electrical v conductor for electricalcurrent passing between the consumable electrode and baseplate or stoolof the rriold. The current heats the electrode and droplets of metalfusing off its lower end fall through the slag to the bottom of the moldwhere a pool of molten metal forms and solidifies upwards from thebottom pool. A refining action takes place in the molten metal as itpasses through the molten slag and, as the electrode is progressivelyconsumed, the refined metal builds up from the bottom of the mold toform an ingot. The molten slag floats on the pool of refined metal andremains in contact with the lower end of the consumable electrode. Therefining process continues until the electrode is consumed orsubstantially consumed.

Slags used in electroslag remelting processes have a high dielectricconstant in the solid form, but are conductive to some extent in theliquid phase. Also, in the molten state, the slag has a low viscosityand slags utilizingcalcium fluoride as one component havea corrosiveeffect on ordinary refractory. For this reason, a furnace for meltingslag prior to its introduction into the mold may be lined with carbon orgraphite in brick or monolithic wall form or both. However, it has beenfound that the graphite or carbon lining, together with the graphiteelectrodes for melting same, are responsible for introduction of carboninto the molten slag which has presented a problem of removing same.Otherwise, the carbon is transferred to the bottom of the ingot whichthus has a higher carbon content than specifications for the steel maycall for and, in any event, different from the carbon content at the topof the ingot.

The known method for reducing the carbon level in the molten slag is toblow oxygen into it; while in the slag furnace. This method is operablebut somewhat unwieldy and it is difficult to estimate when the carboncontent has been lowered by the desired amount. Furthermore the carbonor graphite lining is needlessly oxidized by the excess oxygen, causingearly failure of the lining.

As an experiment, iron oxide was added to themolten slag in the slagfurnace. A highly undesirable foaming action resulted and a crust wasformed on the molten slag. It was found, however, by adding the ironoxide very slowly, the carbon content of the slag could be successfullyreduced in spite of its foaming action and formation of a crust on thetop of the molten slag. The advantages of this method over theintroduction of oxygen were that thequantity of carbon removed was moreeasily gaged and the furnace lining was not detrimentally affected. Butboth methods leave much to be desired in their operational aspects.

SUMMARY OF THE INVENTION I have discovered that if the required amountof iron oxide (mill scale, F6304) is added directly into the mold assoon as practicable after molten slag has been introduced therein andthe melting process has commenced, (the slag being in the molten state)the iron oxide can be added at a relatively rapid rate (within 30seconds to up to five minutes) without causing discernible or harmfulfoaming or crusting of the molten slag around the consumable electrode.The addition of about 0.2% iron oxide removes about 0.034% carbon fromthe molten slag. The slag then has a carbon level of about 0.006 0.016%which is insufficient to affect adversely the quality of the ingotproduced by the process.

Other advantages of the invention will be appreciated from thedescription and with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic view, partlyin section which illustrates the preferred mode of carrying out theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, aconsumable electrode 10 is suspended by a suspension structure 23 in awater cooled copper or steel mold 11. The mold is supported by a baseplate or stool 12 and includes a passageway 18 between the outer shell14 and the inner mold wall 15. The passageway 18 functions to receivethe heat exchange medium 20 for retaining the inner mold wall 15 in anappropriately cooled condition. An inlet 16 and outlet 17 are providedfor the cooling medium 20, preferably water. A cap 21 of molten slag orflux receives the lower end of the electrode 10 and, due to heatgenerated by electric current passing through electrode 10 and cap 21,the lower end of electrode 10 is progressively melted and molten metaldrops 22 fall through the cap 12 to form a molten metal pool 24, which,due to the cooling effects of medium 20, solidifies in the form of aningot 25. The slag blanket or cap 21 is preferably such that it willnot, liberate deletiorious gas either as to quantity or kind during themetal depositing operation and it should not add substantial quantitiesof undesirable ingredients to or remove substantial quantities ofdesirable ingredients from the molten metal. Rather it should flux outimpurities. The molten slag should, furthermore, be such that it willreadily free itself from the molten metal and it has been found that awide variety of slags or fluxes may be used satisfactorily. A calciumfluoride flux has been found advantagous.

The molten slag which comprises the cap 21 may be passed into mold 11from a convenient source of supply such as slag furnace 40 by anysuitable means as it would occur to one skilled in the art such as theconduit 27 which is preferably water cooled and composed of steel. Asshown in the drawing, the conduit 27 enters into the interior of themold 1 1 through a snugly fitting opening in stool 12 (which also hascooling passageways designated 19 for receiving cooling medium 20) andalso through an opening in a starter plate 28 which is disposed betweenthe stool l2 and the lower ends of the mold 11. The function of starterplate 28 is to provide a dependable electric conductor under mold 1 l tohigh alumina refractory bricks 47, an expansion joint 50 comprisingpowdered alumna, a graphite shell 51 which may be integral and have theshape of a cup or be formed of graphite bricks as shown and finally onresistance heating between graphite" electrodes 60. Ad-

ditional dry slag isadded'until the' d es ired amount has beenintroduced into the slag furnace 40 and the temperature of the slag isbrought up to 2800 '2900F.

Although care is taken to introduceonly the amount of slag desired intothe slag furnace 40, there is some variability which appears to beinherent inthe system and, with the knowledge of such variability,electrode is. initially positionedv a shortbut sufficient distance(about 2 inches) from the highest level 'of slag expected tobeintroduced within mold; 11 from furnace 40 in view of prior experienceas to the volumetric parame-, ters of the molten slag charges, The slagfurnace 40 is caused by appropriatemeans (not shown) to tilt about theinterior a layerof graphite or carbon bricks 52. The

roof 54 is composed of a high alumina ram refractory which is tamped inplace to form a monothlic roof structure. The roof includes three mainopenings, an exhaust conduit 55, a feed pipe 56 and a central opening 57which receives three graphite electrodes 60 which are connected to anappropriate electrical power source not shown. Before slag furnace 40 ispivoted about trunnion 42, the electrodes 60 and roof 56 are raised tothe position shown in dot-dash lines.

Dry slag placed within the slag furnace 40 isheated by graphiteelectrodes 60 and due to its resistance is melted whereby the electrodesbecome immersed in the slag which is heated to a temperature of 2800 2900F. for tapping.

It has been'found that slag furnace 40 gives very few problems and maybe used for over 100 heats with bricks 52 replaced every 25 beats moreor less. The graphite working lining comprising carbon or graphitebricks 52 together-with graphite electrodes 60 introduce, however, morethan a desirable amount of carbon into the slag. This carbon, after theslag is introduced into the mold l 1, is transferred to thesteel'forming the ingot 25 so that the carbon content of the ingot isgreater in its lower portion than upper portion.

As previously indicated, it is possible to reduce the carbon level inthe slag by blowing oxygen into the molten slag bath in slag furnace 40or by the slow introduction of an oxide such as an iron oxide to thebath which reacts with the carbon to form carbon monoxide and carbondioxide that is expelled from the molten slag as a gas. Both of thesemethods have definite drawbacks "in that they cause an undue amount offoaming within the slag furnace 40 and also cause a crust to form on topof the slag.

heat causes the gases generated by addition of theoxide to be carriedoff in such a way that harmful foaming action does not occur.

Iron oxide is added at the top of the mold l 1 between the inner moldwall and the sides of the electrode 10 by means of a metering device 61which meters the desired amount of the oxide into the mold via a pipe62..

In operation, dry slag material having a composition of about 40% Cal-30% CaO and 30% A1 0 is added into slag furnace 40 via feed pipe 56 andis melted by trunnion 42 and thus empty them olten slag into the spoutportion 29 of conduit 27 whereupon it enters through said conduit intothe bottomof the mold 11 The slag furnace 40 is tilted to over for thispurpose in order to ensure that it is emptied insofar as possible ofmolten slag. When. the ,slag pouring is complete, electrode l0.isprornpt ly lowered atiaspeed of say 1 inch per 15 30 seconds until itcontacts the surface of cap 21 where-upon ahcurrent flow is immediatelyregistered and .cap 21 becomeshighly liquid within a relatively shortperiod. However, immediately following contact of electrode 10 with cap21, there may rejmain a slight crust at the top of the cap 21 and theadditionof any oxide at'this, time would remain on the crust possiblycausing operating'pr oble'rns by' 'arcing for ex-' ample, although thishas not been experienced. After waiting a period of say 5' minutes whenit is known that the crust 'has disappeared and slag is completelyliquid. The oxide can be added and the desired 'decai burizationreactions proceeds. Accordingly, metering device 61 is then activatedwhereupon the oxide enters the cap 2l via pipe 62 andthe space betweenthe inner mold Wall 15 and" electrode 10.6 g .The amount of iron oxideadded "depends upon the approximate carbon composition of the slag priort6 pouring which, in turn, depends on a number of variables suchasthe'ope'rati'ng te'chiiiciu'e, the temperature of the slag, the slagchemistry, etc. However,-it has been found that two pounds-of iron oxide(Fe O per 1,000 pounds of molten slago'r, in other words, 0.2% issufficient to remove about 0.034% carbon from the slag. Inasmuch as theaverage carbon'content of the slag is usually about 0.04 0.05%, thecarbon level is lowered to a safe or tolerable level; that is, less than0.02% with an aim of about 0.01%, but it is not removed altogether: Inthe event t'oo. much of the oxide is added, the characteristics' of theslag may then believed that the limits of theloxide addition rate shouldbe kept within a range from 0.1% to 1% in order to remove between about0.017 to 0.17% carbon in the case of iron oxide (Fe O r t It has beendetermined that the method as disclosed in thisinvention successfullyreduces the carbon in the slag whereby unduecarbon content in the lowerportion of the ingot 25 is avoided. Whatever'mino'r "carbon "pick -upaffects the bottom r the anger iseventually eliminated through providingpractices;

it can be centered between walls 115 with gaps ofabout 1V2 to 2 inchesin width on each 'side. rurnacq to has a capacity of about 1 /2 tons,ofslag or at least about bring 1,000 pounds of slag to the desiredtemperature. For 2,800 pounds, the requiredtime is about 4 hours.When-electrode contacts the toplof the slag cap 21 a current flow isimmediately registered andan initial voltageof about 90 volts reduceswithin abo ut a few minutes to about 70 voltswith the current being onthe order of about 10,000 amps. The current is a single phase-60 cyclea.c. current; v I .t

Although Fe O lis-preferable because it is readily availableasmillscalefother oxides are thermodynamically capable of causing thedesired reaction. These include Fe O FeO, NiO, M 0 CoO, Cu O,.Cr O MnO,Mn O and Mn 'O particular oxide may-{be chosen wherein the metal elementinvolved may be advantageously added for alloying in the-lower portion:of the ingot, for example,where the lower portion of the electrodecontains less than the desired amount of such element. In thisconnection, it should beunderstood that the metering device 61 is alsoutilized in the process involved fort he selective addition to themolten slag of materials such as lead, molybdenium, aluminum, copper,chromium, and manganese as and when needed to compensate fordeficiencies in the electrode. Moreover, the problem of continuallyadjusting relative movement between theelectrodel0 an'dino ld 11 may bealleviated or, indeed, eliminated by thefladdition" of sufficient steelpellets of desired chemistry of thelike from device 62 during theprocess so that the ingot grows atsubstantially the same rate that the'electrode 10 shortens.

.In practice, electrode may be'energized prior to or as the slag ischarged-into the mold 11, or immediately before lowering same, However,preferably., it is energizedasslag is chargedin to the moldl Also,prefer ably, the slag charging time via funnel portion should notnormally exceed four minutes.

For the purpose of the claims, flux is considered to be included in theterm slag. Also, unless otherwise stated, percentages are by weight.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. An electroslag remelting process which comprises:

melting of slag in a furnace by means of at least one graphite electrodewhereby the carbon content of the molten slag is increased;

transferring said molten slag into the bottom of an electroslagremelting mold wherein an ingot of improved homogeneity is formed by thecontinued melting of a metal consumable electrode the end portion ofsaid electrode being immersed in said molten slag whereby melted metalfrom said end portion falls through said molten slag and solidifies toform said ingot in said mold while an electrical current passes throughsaid slag between said electrode and 'said ingot being formedformaintaining said slag in a molten condition; and 'introducing an'oxidizingagent into said molten slag v "in said mold while said currentis passing therethrough, the amount and rate of said introduction ofsaid oxidizing agent being such as to perform the K function of removingcarbon from said moltenslag we without causing excessive foaming of saidslag. 2. In a method of decarburizing flux havingan under e sired highcarbon content, the flux being used in an 2,800 pounds. It takes about 1/2 to '2 hoursto melt and electroslag remelting process wherein 'it'isin-a molten state in an electroslag' refining mold, the lower portion aconsumable metal electrode immersed in the upper portion of the moltenflux, 'the 'flux being heated by an electrical current flow providedtherethrough, melted metal from the electrode passing through saidmolten flux to the bottom of the mold into a molten metal pool where itsolidifies as a more homogeneous metal, the improvement comprising thestep of adding iron oxide ,to said molten flux in said mold whilecontinuing said current flow whereby decarburiiation of said flux takesplace without excessiveforming of said flux. 7 s 3. Amethod ofaccordance with elairn 2 wherein the .-iron oxide added to said flux isabout 0.2% of the amount of flux by weight. e A I I 4.-A method inaccordance with .claim 3 wherein said iron oxide is mill scale. i i i 5.A method in accordance with claim; 3 wherein said iron oxide isintroduced into said flux within atime range of 30 seconds to 5;minutes,e

6. Anlelectroslag remelting process'which-comprises the steps of: I

- heating a chargeof slag ina slag furnace to a molten 'state'whereinthe slag is exposed to .carbon'and'the carbon content of the slag isincreased toan undesired level; introducing said slag into anelectroslagrefining'mold in 'its'molten' state;

"4"O in rriersi'ngbf the lower end of a' consumable metal electrode intosaid molten slag in said mold andfestablishing an electriccurrent-therethrough which 'is s'ufficient 't'o maintain'said slag insaid mold in a molten state and to melt said electrode immersed Itherein whereby molten metalis received through immediately'with saidslag in a molten state after int roducing same into saidmold adding' anoxidizing agent to said molten sl'ag'while continuing saidcurrentthrough said slag and the melting of said electrode whereby thedecarburization of said slag takes place without excessive foamingthereof and said slag retains its characteristic as a reducing slag. 7.A process according to claim 6 wherein said oxidizing agent is asubstance selected from the group consisting of Feo, Fe O Fe O NiO, M00CoO, Cu O MnO, Mn O and Mn O 8. A process according to claim 6 whereinsaid oxidizing agent comprises iron oxide.

9. A process according to claim 8 wherein said iron oxide is mill scale.10. A process in accordance with claim 6 wherein the amount of oxideadded to said slag is about 0.2% of said slag and is introduced in aperiod of 30 seconds to 5 minutes.

11. An electroslag remelting process which comprises: 1

melting of slag in a furnace which is lined at least in part bycarbonaceous material whereby the carbon content of molten slag isincreased; transferring said molten slag into the bottom of anelectroslag remelting mold wherein an ingot of improved homogeneity isformed by the continued melting of a metal consumable electrodes endportion immersed in said moltenslag whereby melted metal from said endportion falls through said molten slag and solidifies to form said ingotin said mold while an electric current passes through said slag betweensaid electrode and said ingot being formed maintaining said slag in amolten condition;

, and

introducing an oxidizing agent into said molten slag in said mold whilesaid current is passing'therethrough, the amount and rate of saidintroduction a of said oxidizing agent being such as to perform thefunction of removing carbon from said molten slag without causingexcessive foaming of said slag.

12. An electroslag remelting process in accordance with claim 11 whereinafter said molten slag has been introduced into said mold, saidelectrode is lowered into contact with said slag and a current flowthrough said slag is established, the introducing of an oxidizing agentinto said slag being thereafter delayed until the s'lag'between saidmold and said electrode is in a fully fluid condition.

13. An electroslag remelting process in accordance with claim 12 whereinthe period of said delay is about 40 minutes.

14. An electroslag remelting process in accordance with claim 11 whereinsaid oxidizing agent is introduced into said slag within a period ofless than 5 minutes.

" 15. .An electroslag .remelting process in accordance with claim 11wherein said oxidizing agent is a sub- .stanceselected from the groupconsisting of FeO, -Fe O Fe O NiO, M00 C00, Cu O, Cr O MnO, =.Mn O andM11304.

.16. An electroslag remelting process in accordance with claim 11wherein said oxidizing agent consists essentially of iron oxide.

17. An electroslag remelting process in accordance with claim 16 whereinsaid oxidizing agent consists essentially of mill scale.

18. An electroslag remelting process in accordance with claim 1 1wherein said electrical current is an alternating current with a voltageof between about 70 and 90 volts.

. 19. An-electroslag remelting process in accordance with claim 11wherein about 800 watts of power per" pound of slag is being applied tosaid molten slag when lower the carbon content of the molten slag insaid I mold from the range of about 0.04 to 0.05% carbon to a range ofabout 0.006 0.0l6%.

22. An electroslag remelting process in accordance with claim 19 whereinthe oxidizing agent is mill scale and not more thanabout 2 pounds ofsame is introduced to said molten slag for each 1,000 pounds of saidslag.

23. An electroslag remelting process in accordance with claim 22 whereinsaid mill scale is introduced to said molten slag during a period ofabout one-half minute.

24. In an electroslag remelting process of the type wherein slag ismelted in a separate container and sufficient carbon is received by therriolten slag in said container so that the carbon content of the moltenslag becomes undesirably high, said slag subsequently being introducedinto an electroslag refining mold in a molten state, an end portion of ametal consumable electrode being immersed in said molten slag in saidmold and an electrical current going through said slag generating heatto fuse metal from the end of said electrode through the molten slaginto a molten pool of metal at the bottom thereof where it solidifies toform a metal ingot of improved homogeneity the improvement comprisingthe step of adding an oxidizing agent into the molten slag in said moldwhile said current and said molten metal are passing through said moltenslag thereby decarburizing said slag without the occurrence of excessivefoaming of the molten. slag in said mold.

25. In a process according to claim 24 wherein said oxidizing agentcomprises iron oxide. I

26. In a process according to claim 25 wherein said iron oxide is millscale.

27. In a process according to claim 24 wherein said electric current isan alternating'current of about cy-

1. AN ELECTROSLAG REMELTING PROCESS WHICH COMPRISES: MELTING OF SLAG INA FURNACE BY MEANS OF AT LEAST ONE GRAPHITE ELECTRODE WHEREBY THE CARBONCONTENT OF THE MOLTEN SLAG IS INCREASED: TRANSFERRING SAID MOLTEN SLAGINTO THE BOTTOM OF AN ELECTROSLAG REMELTING MOLD WHEREIN AN INGOT OFIMPROVED HOMOGENEITY IS FORMED BY THE CONTINUED MELTING OF A METALCOMSUMABLE ELECTRODE THE END PORTION OF SAID ELECTRODE BEING IMMERSED INSAID MOLTEN SLAG WHEREBY MELTED METAL FROM SAID END PORTION FALLSTHROUGH SAID MOLTEN SLAG AND SOLIDIFES TO FORM SAD INGOT IN SAID MOLDWHILE AN ELECTRICAL CURRENT PASSES THROUGH SAID SLAG BETWEEN SAIDELECTRODE AND SAID INGOT BEING FORMED FOR MAINTAINING SAID SLAG IN AMOLTEN CONDITION: AND INTRODUCING AN OXIDIZING AGENT INTO SAID MOLTENSLAG IN SAID MOLD WHILE SAID CURRENT IS PASSING THERETHROUGH, THE MOLDWHILE SAID CURRENT IS PASSING THERETHROUGH, THE MOLD WHILE SAID CURRENTIS PASSING THERETHROUGH, THE AMOUNT AND RATE OF SAID INTRODUCTION OFSAID OXIDIZING AGENT BEING SUCH AS TO PERFORM THE FUNCTION OF REMOVINGCARBON FROM SAID MOLTEN SLAG WITHOUT CAUSING EXCESSIVE FOAMING OF SAIDSLAG.
 2. In a method of decarburizing flux having an undesired highcarbon content, the flux being used in an electroslag remelting processwherein it is in a molten state iN an electroslag refining mold, thelower portion of a consumable metal electrode immersed in the upperportion of the molten flux, the flux being heated by an electricalcurrent flow provided therethrough, melted metal from the electrodepassing through said molten flux to the bottom of the mold into a moltenmetal pool where it solidifies as a more homogeneous metal, theimprovement comprising the step of adding iron oxide to said molten fluxin said mold while continuing said current flow whereby decarburizationof said flux takes place without excessive forming of said flux.
 3. Amethod of accordance with claim 2 wherein the iron oxide added to saidflux is about 0.2% of the amount of flux by weight.
 4. A method inaccordance with claim 3 wherein said iron oxide is mill scale.
 5. Amethod in accordance with claim 3 wherein said iron oxide is introducedinto said flux within a time range of 30 seconds to 5 minutes.
 6. Anelectroslag remelting process which comprises the steps of: heating acharge of slag in a slag furnace to a molten state wherein the slag isexposed to carbon and the carbon content of the slag is increased to anundesired level; introducing said slag into an electroslag refining moldin its molten state; immersing of the lower end of a consumable metalelectrode into said molten slag in said mold and establishing anelectric current therethrough which is sufficient to maintain said slagin said mold in a molten state and to melt said electrode immersedtherein whereby molten metal is received through said molten slag in amolten metal pool in the bottom of said mold where it solidifies to forma more homogeneous ingot; immediately with said slag in a molten stateafter introducing same into said mold, adding an oxidizing agent to saidmolten slag while continuing said current through said slag and themelting of said electrode whereby the decarburization of said slag takesplace without excessive foaming thereof and said slag retains itscharacteristic as a reducing slag.
 7. A process according to claim 6wherein said oxidizing agent is a substance selected from the groupconsisting of Feo, Fe2O3, Fe3O4, NiO, MoO2, CoO, Cu2O3, MnO, Mn2O3 andMn3O4.
 8. A process according to claim 6 wherein said oxidizing agentcomprises iron oxide.
 9. A process according to claim 8 wherein saidiron oxide is mill scale.
 10. A process in accordance with claim 6wherein the amount of oxide added to said slag is about 0.2% of saidslag and is introduced in a period of 30 seconds to 5 minutes.
 11. Anelectroslag remelting process which comprises: melting of slag in afurnace which is lined at least in part by carbonaceous material wherebythe carbon content of molten slag is increased; transferring said moltenslag into the bottom of an electroslag remelting mold wherein an ingotof improved homogeneity is formed by the continued melting of a metalconsumable electrode''s end portion immersed in said molten slag wherebymelted metal from said end portion falls through said molten slag andsolidifies to form said ingot in said mold while an electric currentpasses through said slag between said electrode and said ingot beingformed maintaining said slag in a molten condition; and introducing anoxidizing agent into said molten slag in said mold while said current ispassing therethrough, the amount and rate of said introduction of saidoxidizing agent being such as to perform the function of removing carbonfrom said molten slag without causing excessive foaming of said slag.12. An electroslag remelting process in accordance with claim 11 whereinafter said molten slag has been introduced into said mold, saidelectrode is lowered into contact with said slag and a current flowthrough said slag is established, the introducing of an oxidizing agentinto said slag being thereafter delayeD until the slag between said moldand said electrode is in a fully fluid condition.
 13. An electroslagremelting process in accordance with claim 12 wherein the period of saiddelay is about 5 - 40 minutes.
 14. An electroslag remelting process inaccordance with claim 11 wherein said oxidizing agent is introduced intosaid slag within a period of less than 5 minutes.
 15. An electroslagremelting process in accordance with claim 11 wherein said oxidizingagent is a substance selected from the group consisting of FeO, Fe2O3,Fe3O4, NiO, MoO2, CoO, Cu2O, Cr2O3, MnO, Mn2O3, and Mn3O4.
 16. Anelectroslag remelting process in accordance with claim 11 wherein saidoxidizing agent consists essentially of iron oxide.
 17. An electroslagremelting process in accordance with claim 16 wherein said oxidizingagent consists essentially of mill scale.
 18. An electroslag remeltingprocess in accordance with claim 11 wherein said electrical current isan alternating current with a voltage of between about 70 and 90 volts.19. An electroslag remelting process in accordance with claim 11 whereinabout 800 watts of power per pound of slag is being applied to saidmolten slag when said oxidizing agent is introduced therein.
 20. Anelectroslag remelting process in accordance with claim 19 wherein saidoxidizing agent is iron oxide and the amount of said iron oxide added tosaid molten slag is about 0.1% of the weight of said slag for each 0.02%carbon to be removed from said flux.
 21. An electroslag remeltingprocess in accordance with claim 20 wherein sufficient iron oxide isadded to lower the carbon content of the molten slag in said mold fromthe range of about 0.04 to 0.05% carbon to a range of about 0.006 -0.016%.
 22. An electroslag remelting process in accordance with claim 19wherein the oxidizing agent is mill scale and not more than about 2pounds of same is introduced to said molten slag for each 1,000 poundsof said slag.
 23. An electroslag remelting process in accordance withclaim 22 wherein said mill scale is introduced to said molten slagduring a period of about one-half minute.
 24. In an electroslagremelting process of the type wherein slag is melted in a separatecontainer and sufficient carbon is received by the molten slag in saidcontainer so that the carbon content of the molten slag becomesundesirably high, said slag subsequently being introduced into anelectroslag refining mold in a molten state, an end portion of a metalconsumable electrode being immersed in said molten slag in said mold andan electrical current going through said slag generating heat to fusemetal from the end of said electrode through the molten slag into amolten pool of metal at the bottom thereof where it solidifies to form ametal ingot of improved homogeneity the improvement comprising the stepof adding an oxidizing agent into the molten slag in said mold whilesaid current and said molten metal are passing through said molten slagthereby decarburizing said slag without the occurrence of excessivefoaming of the molten slag in said mold.
 25. In a process according toclaim 24 wherein said oxidizing agent comprises iron oxide.
 26. In aprocess according to claim 25 wherein said iron oxide is mill scale. 27.In a process according to claim 24 wherein said electric current is analternating current of about 60 cycles.
 28. In a process according toclaim 24 wherein said slag is composed of about 40% CaF2, 30% CaO, and30% Al2O3.